Firefighting nozzles are made in a wide range of sizes and types for different levels of severity of the hazard to be protected or extinguished, and according to the spray type desired by the firefighter. The simplest form of a firefighting nozzle is simply a hole, most generally made to a converging shape that accelerates water to gain velocity needed to project the water to its target. (The term “water” will be used to refer to any fluid used to fight a fire, whether it be plain water, water plus foaming agents, foam, or some other type of liquid.) In this type of nozzle, there is no void in the water at the point of discharge and the resulting jet is sometimes referred to as a “solid stream.” This type of jet will reach a long distance if the water flowing through the nozzle has relatively low turbulence and if water pressure is relatively high, for example in the range of 30 to 150 PSI (about 3 to 10 bar).
While a solid stream jet may be appropriate for many fires, a more dispersed spray pattern is also useful for a variety of needs. Peripheral jet nozzles (also known as fog nozzles) are believed to create sprays with smaller droplet sizes, and it is believed that the smaller droplet size absorbs heat better. Firefighters who are partial to fog nozzles are sometimes partial to fog patterns produced by fog teeth. The fog teeth have an angled face, and water striking that face causes the fog teeth to rotate around the central axis of the nozzle. The gap formed in the spray at each tooth can be seen in high speed photographs.
Many peripheral jet nozzles have a center support within the waterway of the nozzle. (Many garden sprayers use a similar design.) The center support causes the water to discharge from the nozzle with a hole in the center. Many of these nozzles are infinitely variable and can be adjusted to provide anything from a wide fog pattern to a hard-hitting and long-reaching straight stream.
Despite these technologies, some firefighters believe that the hole in the center of a peripheral jet nozzle reduces the effective distance the spray reaches and reduces the ability of the spray to penetrate hot fires to their seat. Thus, many firefighters prefer a smooth bore nozzle (tip) that has no central support and thus leaves no “hole” in the center of the spray. Smooth bores are oftentimes made in sets of two, three, or four nozzles that form a series of converging orifices referred to as a stacked tip. Each smooth bore can be connected to the others in series by a threaded joint and hose gasket. The fireman may choose from any tip size by unthreading tips that are not needed. Some smooth bore nozzles have a constant diameter (instead of a converging diameter). These constant-diameter nozzles are often used for spraying compressed foam.
A smooth bore nozzle does not naturally produce dispersed spray pattern, and many attempts have been made to selectively modify the spray pattern from a smooth bore so that a firefighter can produce a dispersed spray if desired. The modifications have generally been fragile fog producing devices that protrude beyond a heavily modified nozzle. Examples include U.S. Pat. Nos. 53,175, 72,372, 280,759, 553,454, 2337,298 and embodiments shown in U.S. Pat. No. 7,097,120. Nozzles with protruding devices sacrifice the ability to add smaller stacked tips in series beyond the fog producing device. The devices have been seen as prone to clogging with stringy debris. They are also prone to damage during handling, because firefighters sometimes need to use the nozzle at hand to break windows or punch holes in walls, and the nozzles sometimes get tossed to or from a roof.
Devices used to impart rotary motion to the flow from a smooth bore nozzles before the flow is discharged are shown in U.S. Pat. No. 759,320. These nozzles can produce a sprayed jet of water, but cannot produce a straight jet. In addition, obstructions in the center of the waterway block the clear view through the nozzle that smooth bore proponents desire as proof that the nozzle will provide a flow will with no “hole” in the center.
In Europe, particularly Germany, some smooth bore nozzles are fitted with a ball valve having a set of vanes in the center of the ball. The vanes are curved on one end, and the valve operates in any of three positions: straight jet, off, and full fog. When the curved portion of the vanes is downstream, a vortex is formed resulting in a narrow fog pattern from the smooth bore. Although this smooth bore nozzle can produce a fog pattern, the flow has to be interrupted to change spray patterns, and interrupting flow can be dangerous an even life-threatening in a firefighting situation. In addition, the width of the spray pattern is also not adjustable, which is also undesirable.
More recently, the Saberjet and SaberMaster nozzles produced by Akron Brass combine the fog-making ability of a peripheral jet nozzle with the solid stream ability of a smooth bore nozzle by putting a smooth bore nozzle in the center of the fog nozzle, as disclosed in U.S. Pat. No. 6,877,676. The water may be directed to the central smooth bore or to a secondary flow path where water is diverted to form a fog spray. The nozzle looks like a peripheral jet nozzle since the profile of the smooth bore is hidden within the center. This approach was previously shown in older patents including U.S. Pat. Nos. 641,933, 1,251,118, and 2,271,800. These nozzles are relatively heavy and complex compared to peripheral jet nozzles of equal flow. The side channels are quite narrow compared to the central orifice of the smooth bore nozzle, and the secondary flow path is obstructed from plain view, raising concerns that debris may becoming lodged in inaccessible regions. Other operational difficulties arise when transitioning between flow from the smooth bore and flow through the secondary fog channels. Technical difficulties of designing an on/off transition that maintains both a uniform flow, and a seamless spray pattern transition have yet to be surmounted. As a result, the “smooth bore within a fog nozzle” concept remains flawed.
Some firefighters address the problem of not being able to produce dispersed spray from a smooth bore nozzle by partially closing a valve just upstream of the nozzle to create violent turbulence. The turbulence creates a pseudo-fog pattern. For example, a half-way closed ball valve can generate a narrow dispersed spray pattern of about 20 degrees included angle. However, partially closing the valve significantly reduces flow, which in turn sacrifices cooling and extinguishing capacity. Reducing flow through a fixed orifice also reduces nozzle pressure, which decreases spray velocity and increases droplet size resulting in poor performance.
Adjusting fog sprays while fighting a fire should be simple and quick. Systems that require a firefighter to change devices to vary a fog spray are of little value. There is a need for a new type of straight bore nozzle; a simple, rugged device that a firefighter can easily and smoothly adapt between providing a smooth bore flow and a range of fog spray patterns.